Re: 7mm stw build finlley order it last week
Depending on the distances you plan to shoot, the 20 MOA will put your scope more optically centered than the 30 MOA.
I personally don't have a 20MOA rail on my 7 STW and don't have any trouble dialing out to 800-1000yards with my Huskemaw scope.
So, my feeling is that the 30 MOA rail is alittle overkill.
As far as the 56mm objective I feel it might mount to high for you, and that you would be happier with the 50mm.